Differentials are known in the automotive industry as devices that split engine torque two ways, allowing each output to spin at a different speed. Generally, differentials have three primary tasks: to aim the engine power at the wheels; to act as the final gear reduction in the vehicle, slowing the rotational speed of the transmission one final time before transmission to the wheels; and to transmit the power to the wheels while allowing them to rotate at different speeds.
In a typical vehicle application, the rotating driveshaft of the vehicle engages a ring gear, which is mounted onto the differential housing. Thus, the driveshaft drives the ring gear, which in turn rotates the differential housing. A typical mechanical differential contains a housing (or carrier), two side gears, and several pinion gears. Pinion shafts attach the pinion gears to the housing so that, as the housing rotates, the pinion gears are driven. The pinion gears drive the two side gears, which in turn drive the axle (or half shafts) attached thereto.
Referring now to FIGS. 1-3, a known differential assembly 1 is shown. A differential housing 2 having holes 20 for receiving a pinion shaft 22a. Specifically, each pinion shaft 22a is inserted into the holes 20. The pinion shaft 22a is secured to the housing 2 via one or more locking pins 25 extending through the pinion shaft 22a and into the housing 2. The locking pins 25 secure the pinion shaft 22a so that the pinion gears 8 meshingly engage side gears 19. The locking pins are typically required to lock the pinion shaft to the housing so as to prevent movement of the pinion shaft with respect to the differential housing. The use of locking pins in this manner requires holes to be bored into the housing and pinion shafts, and can increase the time and costs associated with manufacturing and assembling the differentials. Significant machining and complex assembly is needed for such known locking differentials.
Extending from each side gear 19 is an axle shaft 40 of a vehicle (not shown). In known differential housing assemblies, a drive shaft extends longitudinally through a centerline of the vehicle and connects to a ring gear attached to the differential housing 2. As the drive shaft rotates the ring gear, the differential housing 2 rotates and, in turn, the pinion shaft 22a rotates. The rotating pinion shaft 22a rotates the pinion gears 8 which engage the side gears 19 and drives the axles 40. Due to the arrangement of the differential housing 2, the pinion shaft 22a is orientated off-center with respect to the vehicle thus resulting in each axle shaft 40 having a different length.
Axle shafts 40 of different lengths are undesirable as each axle shaft 40 must be manufactured separately. In addition, each axle shaft 40 must be machined to precisely the length required for engagement with the respective side gears 8. Further, each axle shaft 40 must be sorted and assembled on the corresponding side of the vehicle. Moreover, if each axle shaft 40 is of a different length, then each axle shaft 40 will experience a different amount of torque or “wind up”. Over time, the axle shafts 40 may deform or otherwise be damaged by such unequal lengths and thus inherent different torque amounts. In addition, the operator of the vehicle may experience torque steer and/or squirm from the torque applied to unequal axle shaft lengths.
Accordingly, there is a need in the art for a differential housing capable of being offset from the centerline of the vehicle while being arranged to allow equal length axle shafts. Moreover, there is a need to provide a housing capable of supporting pinion shafts without the use of locking pins and associated manufacturing operations and components.